introduction
In recent years, mobile phones are no longer a simple communication tool. It has become a portable entertainment tool, and it is expected to develop into a reliable payment tool in the future, and it is convenient and quick to complete payment through mobile phones in the fields of consumption, shopping, transportation, and the like. Based on the new demand of mobile phones, mobile payment came into being, and gradually became a hot issue for mobile operators, mobile phone manufacturers and SIM card manufacturers. There are many solutions for mobile payment, among which the dual interface SIM card solution and the Near Field CommunicaTIon (NFC) solution are more feasible. The dual-interface SIM card solution has been available, and the short-range communication solution is in the development stage.
The dual interface SIM card solution enables contactless communication by adding a contactless IC card interface to the SIM card. The antenna is connected to the two interfaces C4 and C8 that are not used by the SIM card. The dual-interface SIM card adds the functionality of a non-contact IC card to the phone, but does not implement a reader and peer-to-peer communication. NFC is an ultra-short-range wireless communication technology proposed by NXP and Sony that enables intuitive, convenient, and secure communication between two NFC-compatible devices. The main application of NFC is mobile micropayment, and it can also be applied to areas such as access control and public transportation.
Compared with the dual interface SIM card solution, the advantages of the NFC solution are reflected in the following aspects:
1 NFC solution can achieve more applications;
2 The connection between the NFC chip and the SIM card uses the C6 (SWP) contact, which does not affect the high speed air data download of the SIM card;
3 NFC solution is a complete solution to provide reliable, secure and convenient communication;
4 The NFC solution is fully compatible with existing readers and does not require any changes to the reader.
In summary, NFC is the most feasible solution for mobile contactless payment services, while the SWP connection solution is part of NFC technology.
1 Overview of Near Field Communication
Short-range communication is a short-range non-contact type that operates in the 13.56 MHz band and has a transmission distance of less than 10 cm. The transmission speed can now reach 106 kbps, 212 kbps, and 424 kbps, and the ideal rate can reach about 1 Mbps. NFC uses the same frequency as the current popular contactless smart card, and is compatible with ISO14443 A/B-based inductive contactless communication, as well as Philips' MIFARE technology and Sony's FeliCa technology.
1.1 Principle of short-range communication
According to the ISO18092 standard, short-range communication can work in active mode and passive mode. Before communication, you can select one of the transmission rates of 106 kbps, 212 kbps, and 424 kbps, and you can switch between the three.
1.1.1 Passive mode communication principle
In passive mode, the communication principle of short-range communication is the same as that of RFID, which relies on the principle of electromagnetic induction coupling to complete communication. NFC phones have an NFC chip with an antenna built in to receive and transmit wireless data.
When NFC works in passive mode, the reader initiates NFC communication, called an NFC originating device (master device), which provides a radio frequency domain throughout the communication process. The NFC originating device selects one type of transmission data at three rates, and the ISO 18092 standard specifies the modulation and coding techniques used for each transmission rate. The NFC target device (slave device) does not have to generate the radio frequency domain, but uses load modulaTIon technology to transmit data back to the initiating device at the same speed. This communication mechanism is compatible with non-contact smart cards based on ISO14443 A/B, Mifare and FeliCa. Therefore, in passive mode, NFC-initiating devices can detect contactless smart cards or NFC target devices with the same connection and initialization process, and Establish a connection.
In terms of near-field communication applications, there are three application modes: tag mode, reader mode, and peer-to-peer mode. The tag mode, that is, the NFC chip is used as a passive device, and functions as a transponder. In order to ensure the security of the data, after the mobile phone is replaced, the key information is not reset, and the key information of the mobile payment needs to be saved in the SIM card. Communication devices include readers, NFC chips, and SIM cards. At this time, the NFC chip provides a radio frequency interface and is responsible for forwarding radio frequency data to the SIM card. For the SIM card, there is no need to add a contactless interface like a dual interface SIM card, and a connection to the NFC chip is implemented using the SWP interface. In tag mode, the NFC chip is similar to a bridge, forwarding data between the reader and the SIM card.
The NFC chip is a chip embedded in a mobile phone and is powered by the power system of the mobile phone. In order to ensure the normal operation of mobile payment when the mobile phone is out of power, the tag mode needs to support passive work, and its working principle is based on electromagnetic induction. The antenna coil of the reader produces a high frequency, strong electromagnetic field that passes through the cross section of the coil and the space around the coil. A portion of the magnetic field lines that emit the magnetic field pass through the antenna coil of the transponder at a distance from the reader coil. A voltage is generated on the antenna coil by induction, rectified and supplied as a power source to the NFC chip and the SIM card.
1.1.2 Principle of Active Mode Communication
In the active mode, when the NFC initiator sends data to the target device, it must generate its own RF field. When the read NFC device sends a response to the initiator, it also generates its own RF field. Both the initiating device and the target device generate their own RF field, which is the standard mode for peer-to-peer network communication and allows very fast connection settings.
Mobile devices work primarily in passive mode, which dramatically reduces power consumption and extends battery life. Active mode is mainly for point-to-point mode, used for data exchange between notebooks, mobile phones, and digital cameras.
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